1. Atoms

2. Electrons – negatively charged part of atom found in electron clouds
Atomic Structure
Electrons – negatively charged part of atom found in electron clouds
Nucleus – positively charged center
Protons – positively charged particles in the nucleus
Neutrons – particles in the nucleus that have no charge; neutral
Charge of protons and electrons are opposite but equal, so their charges cancel each other out.

3. Atoms of different elements contain different numbers of protons
Atomic Number – number of protons in an atom
Ex: Carbon – atomic number is 6
6 protons, 6 electrons

4. Atomic Mass/Mass Number – Total number of protons and neutrons in an atom. Ex: Carbon – mass number is 12, atomic number is – 6 = 6 There are six neutrons.

5. Example Boron – Atomic Number is 5
Atomic Mass is 11 (10.81 rounds to 11)
Protons = 5
Electrons = 5
Neutrons = 11-5 = 6

6. Let’s draw the Boron atom:
5 protons
5 electrons
6 neutrons
Nucleus – protons and neutrons
electrons - - - + + + N + + - - N N N N - N - - -

7. Quick Check!
Draw a NITROGEN atom with the correct number of protons and neutrons in the nucleus and the correct number of electrons in the electron cloud.

8. Quick Check!
Draw a Fluorine atom with the correct number of protons, neutrons, and electrons. - - - - - - + N - - - - - - - - - -

9. Isotopes
Isotopes are atoms of the same element that have different numbers of neutrons.
Ex: Carbon (C) atoms
Always have 6 protons
Naturally occurring Isotopes of carbon
6 neutrons (most common)
7 neutrons
8 neutrons

10. Mass of an Atom
The mass is so small that scientists made up a new unit. Atomic Mass Unit (amu) 1 proton ~ 1 amu 1 neutron ~ 1 amu 1 electron ~ 0 -> the mass of electrons has very little effect on the atom’s total mass

11. Mass Number = # of Protons + # of Neutrons Ex: Carbon Mass Number = 6 protons + 8 neutrons Mass Number = 14 Carbon-14 Carbon -13 Carbon-12 (most common)

12. Ex2: How many protons, neutrons, and electrons are in Neon-22
Ex2: How many protons, neutrons, and electrons are in Neon-22? Atomic Number = 10 Protons = 10 Protons + Neutrons = Mass Number 10 + ______ = 22 Neutrons = 12 How many electrons are in this isotope? 10

13. Ex3: How many protons, neutrons, and electrons are in Nitrogen-15
Ex3: How many protons, neutrons, and electrons are in Nitrogen-15? Atomic Number = 7 Protons = 7 Electrons = 7 Neutrons = 8 Protons + Neutrons = Mass Number 7 + _______ = 15

14. Unstable or Radioactive Isotopes
Some isotopes are unstable or radioactive – atoms that spontaneously fall apart after a certain amount of time, giving off radiation. Radiation can damage or destroy living cells.

15. Radioactive Isotopes Cobalt – 60 Protons: 27 Neutrons: 33
Electrons: 27
Mass Number: 60
Use: irradiating food (kills bacteria)

16. The more neutrons in an isotope, the more mass it has, the easier it is to break apart – the more likely it is radioactive Half-life – the time it takes an atom to decay

17. Isotopes may also be written like this…
3He Helium-3
23Na Sodium-23
Mass number

18. Quick Check!
What is the name of this isotope? (Draw a diagram of this isotope in your notebook.)
Protons
Neutrons
Electrons

19. Particle Accelerator (Atom Smasher) – used to make synthetic (man made) atoms

20. Ions
Ions – an atom that is no longer neutral because it has gained or lost electrons

21. Positive ions – when electron(s) are lost -more protons than electrons Helium 𝑯𝒆 +

22. Negative ions – when electron(s) are added or gained -more electrons than protons Helium 𝑯𝒆 − + + N - -

23. Ex1: Positive or Negative Ion. Positive ion Why
Ex1: Positive or Negative Ion? Positive ion Why? B/c there are more protons than electrons (more positive than negative charges) Which element? Lithium Li+ N - + N + N + -

24. Ex2: Positive or Negative Ion
Ex2: Positive or Negative Ion? Positive ion How many electrons were lost? 2 Which element? Boron B2+ + - N N - + N + N N + + -

25. -
Ex3: Positive or Negative Ion? Negative ion How many electrons were added? 1 Which element? Boron B- + - N N - + N + N N + - + - -